1. Field of Invention
The present invention relates to the field of multipoint audio/video conferences, and more particularly to improving the quality of the conference by reducing nuisance signals.
2. Description of Background Art
Multipoint conferences of audio, video, and/or multimedia involve communication between more than two participants. Commonly, conference calls may be established over a communications network, such as the Public Switched Telephone Network (“PSTN”), an Integrated Services Digital Network (ISDN), an Internet Protocol (IP) network, etc. The network contains Multipoint Control Units (MCU) and/or audio bridges that route and compose the communications of the participants in the call. The operation of MCUs and audio bridges are well known to those skilled in the art, and exemplary audio bridges are disclosed in U.S. patent application Ser. Nos. 10/072,081 and 10/144,561, the contents of which are incorporated herein by reference. It should be noted that the terms “MCU” and “audio bridge” may be used interchangeably herein.
A common MCU may receive audio signals from a plurality of conferees, analyze the signals and create control information such as, but not limited to, VAD (Voice Activity Detection), signal energy, and signal quality measures. Based on the control information, decisions may be made regarding whose signals will be mixed and distributed among the other conferees, or whose signal will be muted due to a conclusion that the signal is below acceptable quality. Un-Acceptable Signal (UAS) is an objective criteria and may depend on the type of the conference. Exemplary criteria may be non-voice signals such as: music, DTMF, background noise, etc. The terms “noisy signal,” “nuisance,” and “UAS” may be used interchangeably, and the term “nuisance” may denote all of these terms.
There are known methods for generating information regarding signal energy, VAD, and quality. Exemplary algorithms for creating such information are disclosed in G723.1 (used in Annex A for the same standard); G729.1 Annex B; and GSM AMR (GSM 06.71) using the VAD algorithm GSM 06.94. A simple algorithm for a Nuisance Detector (ND) may define a signal as “nuisance” when the signal energy (SE) is above a certain level, while the VAD indicates that the signal is not voice.
The quality of a conference depends on the automatic decisions made by such methods. For example, a sensitive ND algorithm may disconnect a valid participant, while a less sensitive algorithm may add a noisy connection to the conference mix, i.e., the composed audio signal of the selected conferees. The selection is based on the conference setup parameters and on the automatic decisions made from analyzing the signals of the current speakers. There are cases where an automatic decision may frequently reach an erroneous result. For example, in the case where a conferee places the conference call on hold and accepts another call, the private branch exchange (PBX) to which the conferee is connected may play “music on hold” over the conferee's connection, disturbing the rest of the conference's participants. “Music on hold” may be music, broadcast radio, advertising or other signals to the on-hold conferee. Generally “music on hold” may have the same properties as speech and therefore it may pass the criteria of common VAD and/or ND algorithms and therefore may erroneously be transmitted to the other parties in the conference. On the other hand, a sensitive ND that is not properly tuned to the connection quality of a certain conferee may harm/disconnect a valid conferee. Therefore, it is difficult to pre-tune the ND algorithm to different conferee's conditions.
Thus, it is evident that current technologies of automatic nuisance detection in audio/video conferencing may make wrong decisions that reduce the quality of the conference. Therefore, there is a need in the art for a new nuisance detection method to overcome these deficiencies.